Drusen and Macular Degeneration

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Macular degeneration is a progressive eye disease that affects the tiny, central part of the retina called the macula at the back of the eye and can cause loss of central vision. Macular degeneration can occur in either or both eyes. The disease can develop at any age, but is far more common in people over 60 which is why it is often referred to as age-related macular degeneration, or AMD for short.  It is the leading cause of vision loss in people over 40.

AMD does not affect peripheral (side) vision and does not result in total blindness. However, progressive central vision loss can seriously impact everyday life for AMD patients. 

Those with more serious vision loss experience difficulty with reading, driving, seeing and recognizing faces, playing sports, close-up work, watching television, daily functional needs like cooking, selecting clothing, hygiene, and really, any activity requiring central vision, which is most.

Dry AMD is a broad term that covers all forms of AMD that are not wet AMD.  In dry AMD, waste material, generated by the intense metabolic activity of photoreceptors in the retina, accumulates behind the macula and forms deposits called drusen.  In older people, having some, smaller drusen is considered normal, but in a person with AMD the body’s waste removal system cannot adequately remove this material, and over time the drusen increase in number and size. 

Drusen are made of fats combined with proteins (much like the plaque that line blood vessels in cardiovascular disease), and they hinder the absorption of nutrients that normally are delivered to the photoreceptors by the capillary-rich tissue of the retina called the retinal pigmented epithelium (RPE).  With less access to necessary nutrients, photoreceptors start to die, which leads to reduced visual acuity, color vision and also to a loss of contrast sensitivity.  When drusen become larger, they can physically push photoreceptors out of their normal position, which can create distortion that causes straight lines to appear wavy.  When enough photoreceptors die, a dead zone appears in our central visual field.

According to the American Academy of Ophthalmology, drusen are not the underlying cause of AMD, but the presence of a significant number of large, soft drusen is a sign of dry AMD. 

Dry AMD is also referred to as atrophic AMD because it causes a thinning — or atrophy — of the macula.  Non-exudative AMD is another term for dry AMD, which simply means that it is not wet (exudative) AMD.

While no treatments currently are available for dry AMD, several are in clinical trials and may soon reach patients.  Until then, the best way to manage dry AMD is to slow its progression by making risk-reducing lifestyle choices: stop smoking, eat an AMD-beneficial diet, maintain proper weight and blood pressure, exercise, and protect your eyes from the damaging light of the sun.

Progression to the wet form of AMD happens in about 10-15% of AMD patients. It is called “wet” due to the development of leaky blood vessels that have grown to compensate for the functional problems created by the dry form of AMD.  The excessive growth of these leaky blood vessels is called neovascularization, which is why wet AMD is also called neovascular AMD, or nAMD for short.

Treatments exist for wet AMD that can stop the development of leaky blood vessels by interfering with the body’s signaling for new blood vessel growth.  These treatments require injections into the eye of drugs called anti-VEGF agents, at regular intervals that you establish with your eye doctor. Over time, based on how you respond to the treatments, your retina specialist may suggest that the time between them can be extended.  A new class of treatments, that combine anti-VEGF agents with agents that also reduce leakage from existing blood vessels, is becoming available.

While treatments for wet AMD are designed to preserve current sight and prevent further vision loss, some patients can experience improved visual acuity as fluids that have leaked behind the retina are reabsorbed and the macula resumes its normal position.

The transition to wet AMD can be sudden, accompanied by dramatic central vision loss.  This can be avoided to a great extent if you work closely with your eye care specialist to monitor the progression of your dry AMD (both at home, using self-testing tools, and through regular office visits) and report any changes to your vision right away. The same holds true for monitoring your wet AMD and not missing treatment appointments, which can allow the disease to progress.